Diagnosis
The main battery isn't delivering power to the system. This is almost always a loose or disconnected internal connector, not a dead battery.
How to Fix It
Reseat the main power connector inside the deck. Remove the eight deck screws, lift the deck plate, locate the large white plug from the battery to the controller, disconnect it, clean the contacts with a dry cloth, and firmly reconnect it. Secure the deck plate back.
If That Didn't Work
The battery management system (BMS) might have entered a protective lockout. Leave the scooter on the charger for 12+ hours, then try holding the power button for 10 seconds.
Heads Up
Do not probe or bypass any battery connections with metal tools—you risk a short circuit. If you see any swollen or damaged battery cells, stop and contact Apollo immediately.